Description

The FPC <x> reports 'temperature low alarm' and 'temperature low warning' frequently on MX, QFX, and PTX platforms.

This is a known hardware issue with some of the Finisar 40g optics.

Symptoms

The following messages are generated frequently and repeatedly with 40GE interfaces: 

Jun 25 09:45:09  MX480 fpc0 qsfp-0/1/0: Temperature low alarm set
Jun 25 09:45:10  MX480 fpc0 qsfp-0/1/0: Temperature low warning set
Jun 25 09:45:19  MX480 fpc0 qsfp-0/1/0: Temperature low alarm cleared
Jun 25 09:45:19  MX480 fpc0 qsfp-0/1/0: Temperature low warning cleared
Jun 25 12:45:27  MX480 fpc0 qsfp-0/1/0: Temperature low alarm set
Jun 25 12:45:27  MX480 fpc0 qsfp-0/1/0: Temperature low warning set
Jun 25 12:45:36  MX480 fpc0 qsfp-0/1/0: Temperature low alarm cleared
Jun 25 12:45:36  MX480 fpc0 qsfp-0/1/0: Temperature low warning cleared
Jun 25 13:07:08  MX480 fpc0 qsfp-0/1/0: Temperature low alarm set
Jun 25 13:07:08  MX480 fpc0 qsfp-0/1/0: Temperature low warning set
Jun 25 13:07:17  MX480 fpc0 qsfp-0/1/0: Temperature low alarm cleared
Jun 25 13:07:17  MX480 fpc0 qsfp-0/1/0: Temperature low warning cleared
Jun 25 13:29:33  MX480 fpc0 qsfp-0/1/0: Temperature low alarm set
Jun 25 13:29:33  MX480 fpc0 qsfp-0/1/0: Temperature low warning set
Jun 25 13:29:42  MX480 fpc0 qsfp-0/1/0: Temperature low alarm cleared
Jun 25 13:29:42  MX480 fpc0 qsfp-0/1/0: Temperature low warning cleared
Jun 25 16:02:19  MX480 fpc0 qsfp-0/0/0: Temperature low alarm set
Jun 25 16:02:19  MX480 fpc0 qsfp-0/0/0: Temperature low warning set
Jun 25 16:02:28  MX480 fpc0 qsfp-0/0/0: Temperature low alarm cleared
Jun 25 16:02:28  MX480 fpc0 qsfp-0/0/0: Temperature low warning cleared
Jun 25 20:38:07  MX480 fpc0 qsfp-0/1/0: Temperature low alarm set
Jun 25 20:38:07  MX480 fpc0 qsfp-0/1/0: Temperature low warning set
Jun 25 20:38:16  MX480 fpc0 qsfp-0/1/0: Temperature low alarm cleared
Jun 25 20:38:16  MX480 fpc0 qsfp-0/1/0: Temperature low warning cleared
Jun 25 22:19:00  MX480 fpc0 qsfp-0/1/0: Temperature low alarm set
Jun 25 22:19:00  MX480 fpc0 qsfp-0/1/0: Temperature low warning set
Jun 25 22:19:09  MX480 fpc0 qsfp-0/1/0: Temperature low alarm cleared
Jun 25 22:19:09  MX480 fpc0 qsfp-0/1/0: Temperature low warning cleared

User@MX480> show chassis hardware |find FPC

FPC 0            REV 42   750-056519   CAFK8162          MPC7E 3D MRATE-12xQSFPP-XGE-XLGE-CGE
  CPU            REV 20   750-057177   CAGM3673          SMPC PMB
  PIC 0                   BUILTIN      BUILTIN           MRATE-6xQSFPP-XGE-XLGE-CGE
    Xcvr 0       REV 01   740-052009   US20SC6           QSFP+-40G-LR4
  PIC 1                   BUILTIN      BUILTIN           MRATE-6xQSFPP-XGE-XLGE-CGE
    Xcvr 0       REV 01   740-052009   US20SAB           QSFP+-40G-LR4

Solution

This issue has been analyzed as a Finisar specific 40g optics H/W issue. The temperature low is a false alarm due to the sub-optimal filtering logic in the optics internal circuit that might pick up unnecessary signals.

User@MX480> show chassis pic fpc-slot 0 pic-slot 1
FPC slot 0, PIC slot 1 information:
  Type                             MRATE-6xQSFPP-XGE-XLGE-CGE
  State                            Online
  PIC version                  0.0
  Uptime                         15 days, 8 hours, 23 minutes, 30 seconds

PIC port information:
                         Fiber                    Xcvr vendor       Wave-    Xcvr         JNPR
  Port Cable type        type  Xcvr vendor        part number       length   Firmware     Rev
  0    40GBASE LR4       SM    FINISAR CORP.       FTL4C1QE1C-J1     1301 nm  0.0          REV 01

Port speed information:

  Port  PFE      Capable Port Speeds
  0      1       4x10GE, 40GE

This false alarm issue has been fixed in the optics component and the manufacturer (Finisar) has modified the qsfp firmware to better handle the false signal on the newer optics.

The following is recommended:

  1. Ignore the alarm unless the optics fails because the issue is a cosmetic one due to wrong reading of register bit in qsfp.  There is no impact to the data communication.
  2. Suppress the messages by following the instructions in KB9382 - How to prevent certain syslog messages from being written to the log file [juniper.net]

Modification History

2021-10-04: Added QFX and EX series to product categories.
2022-02-25: Removed the repeated o/p for SFP